1. Field of the Invention
The present invention relates to a technique for personal authentication by use of biometric information.
2. Description of the Related Art
A technique for personal authentication by use of biometric information has become widespread. There has been a demand that even a small portable device be provided with a function for acquiring biometric information. A line sensor is an example of a unit having such a function. For example, in a fingerprint authentication technique, a line sensor acquires an image of a fingerprint of a finger moving on the sensor as a plurality of line-shaped images. The entire fingerprint image can be generated by combining the plurality of line-shaped images acquired by the line sensor. A line sensor has a smaller sensor area as compared to a sensor capturing an entire fingerprint image at a time, thereby enabling space-saving upon mounting on a small portable device (see, for example, Japanese Patent Laid-Open Publications Nos. 2001-155137 and 2003-259116)
However, a line sensor generally captures a large number of line-shaped images per unit time. Thus, when the moving speed of a finger is slow, the sensor captures multiple images of a portion of a fingerprint. Therefore, if the captured line-shaped images are combined without being processed, the combined image is caused to be elongated.